Mixed alumina dispersions

ABSTRACT

MIXED ALUMINA COMPOSITIONS COMPRISING POSITIVELY CHARGED COLLOIDAL AQUEOUS DISPERSIONS WHOSE SOLIDS CONTENT COMPRISES 25 TO 75% OF A FIRST ALUMINA COMPONENT HAVING AN ULTIMATE DISPERSED PARTICLE SIZE NO MORE THAN ABOUT ONE-FIFTH AS GREAT AS A SECOND ALUMINA COMPOSITION COMPRISING 75-25% OF THE SOLIDS CONTENT, AND METHOD FOR THEIR USE AS ANTI-SLIP OR PITCH CONTROL AGENTS IN PAPER MANUFACTURING.

United States Patent ABSTRACT OF THE DISCLOSURE Mixed alumina compositions comprising positively charged colloidal aqueous dispersions whose solids content comprises 25 to 75% of a first alumina component having an ultimate dispersed particle size no more than about one-fifth as great as a second alumina composition comprising 75-25% of the solids content, and method for their use as anti-slip or pitch control agents in paper manufacturing.

BACKGROUND OF THE INVENTION Field of the invention This invention relates to mixed alumina compositions. More particularly, this invention relates to mixed alumina compositions of different particle sizes and to their use in paper manufacturing.

Description of the prior art Methods for economically controlling pitch in paper mill systems have been intensely studied for many years. While only a small portion of available pitch actually recirculates in the white water, this is often present in amounts great enough to agglomerate at various locations, necessitating frequent shutdowns for cleaning purposes. Disper" *ntsalone'are generally ineffective for this purpose,"since they merely function to keep the pitch in suspension while its concentration builds up.

'By maintaining the concentration of pitch in the white water below critical levels, the formation of deposits can be substantially reduced. The addition of floeculating agents such as talc, diatomaceous earth and the like has met with limited success, since the excessive use of such materials 'tends to weaken and discolor the sheet.

"Recently several investigators have reported on the use of colloidal aluminas as paper pitch control agents. While offering significant advantages Over other methods, the cost effectiveness of these materials has not been sufficient to induce widespread acceptance in the industry. In addition to their use 'as pitch control agents, colloidal aluminas have been used as anti-slip agents for frictionizing paper surfaces. Due to the positive electrostatic charge Of colloidal aluminas, they are strongly attracted to negatively charged surfaces such as pitch particles and paper surfaces. Since the aluminas are water compatible, handling and cleanup problems encountered with silicate colloids are minimized.

,degrees'or' so, as determined by accurate testing, may

have significant effects on the ultimate suitability of the papers for various applications.

SUMMARY OF THE INVENTION Accordingly, it is an Object of this invention to provide a composition and method for controlling pitch in paper mills.

Another object of this invention is to provide a com position and method for imparting anti-slip properties to smooth surfaces.

A further Object of this invention is to provide a composition Of mixed aluminas having a higher electrostatic charge than either component alone.

An additional object of this invention is to provide a composition of mixed aluminas having synergistic properties as compared to the individual components.

Other additional uses such as for paper mill retention aids and anti-static agents for rugs or similar surfaces will be obvious to those skilled in the art.

Briefly, these and other objects, features, and advantages of the present invention are provided by mixed alumina compositions comprising positively charged colloidal aqueous dispersions whose solids content comprises 25-75% of a first alumina composition having an ultimate dispersed particle size no more than about one-fifth as great as a second alumina composition forming the remainder of the solidscontent. The dispersions preferably contain 1 to 15% solids content and have a pH of 0 to 6. These compositions have particular utility in controlling paper mill pitch, and in providing anti-slip properties to smooth surfaces such as highly calendered paper surfaces.

BRIEF DESCRIPTION OF THE DRAWING DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS In accordance with the present invention, the preferred mixtures comprise about 25-75% of a first alumina coinposition having a particle size of about 4-6 mp1, a surface area of about 300 m. /gm., and a purity of at least about 99% dry Weight alpha alumina with a second alumina composition having a particle size of about 20-30 mp, a surface area of about 100 m./gm., and a purity of at least about 97% dry weight alumina; The ultimate dispersion is prepared by adding l'to 15%, preferably 3 to 6% and especially about 4%, of the alumina mixture to an acidified aqueous system having a pH of 0 to 6, preferably 3 to 4.

Conventional additives such as anti-foam agents, cationic or non-ionic surfactants, corrosion inhibitors, freezethaw stabilizers, and the like may be added in customary proportions. Since the aqueous colloidal dispersion carries a positive charge, the use of anionic surfactants or other additives is generally to be avoided because such additives tend to result in poor or broken emulsions.

Thecritical feature of the instant invention resides in the mixture of aluminas having vastly different ultimate dispersed particle sizes, that is, at least one of the aluminas having an ultimate dispersed particle size no more than about one-fifth of the other, with about a 25-75% ratio of the first in the mixture. The individual particle sizes, specific surface areas, purities, percent total solids content in the dispersion, and pH of the dispersion as dis cussed above and hereinafter provide optimum properties, but as will be be seen from the attached graphs, it is the use of a mixed particle size that provides unexpected results.

In FIG. 1 the solid lines graphically illustrate the straight-line average slip angle in degrees to be anticipated from a mixture of two materials having generally the same ultimate particle sizes while the broken lines illustrate the actual average slip angles in degrees obtained from such mixtures. It will be seen that, in every instance, the mixed compositions provide a result substantially below that to be anticipated.

In contrast, by reference to FIG. 2 is will be seen that by mixing aluminas having substantially different ultimate dispersed particle sizes, on the order of 5: 1, the resultant d anti-slip agent, for the most part, provides average slip angles substantially above that to be anticipated. Such a phenomenon is quite unexpected.

Again, while the specific materials described below are not to be limiting on the instant inventive concept, the following properties are set forth as preferred:

Alpha alumina compositions are preferably used as the first alumina component of the present invention and such materials are commercially available. For example, the material identified as Dispal M is quite satisfactory. Preferably the first alumina has an ultimate dispersed particle size (the particle sizes are always referred to herein in a dispersion since upon drying these materials tend to agglomerate) of 2 to m diameter, preferably about 4 to 6 mg.

The second alumina component of the present invention may be of any form but preferably is of other than the alpha form. Particularly suitable are gamma and delta fumed aluminas. Commercially available materials identified as Alon C and Aluminium oxide C are quite suitable, the Alon C providing even better slip angles as seen in FIG. 2. Particle sizes of 10 to 100 m diameter, preferably of to m are preferred.

The two aluminas are admixed in a ratio of 25 to 75% by weight of the first alumina with correspondingly 75 to 25% by weight of the second alumina. Optimal proportions can readily be determined for particular application, but will generally contain from to 65% by weight of each alumina. Particularly goods results for many applications are obtained with 50-50 mixtures. The greater electrostatic charge and resistant to slip resulting from the admixture of small and large alumina particles will necessarily be somewhat different for different ratios and the optimum effect will have to be determined for each application. Close packing or loose packing of such minute particles of greatly varying shapes may result in varying resistance to slip and electrostatic charge.

The colloidal aqueous dispersions of the present invention are prepared by standard methods, generally to a stock mixture having a high solids content of about 10 to by weight which may be diluted with water to a solids content of about 1 to 15% by weight, preferably about 4 to 9% for subsequent use or the alumina powders may be added to acidified water having a pH of 2 to 6, preferably 3 to 4, and agitated. Suitable acids include hydrochloric acid, acetic acid, monochloroacetic acid, nitric acid, hydroxyacetic acid, sulfamic acid and the like; halogenated acids are preferred as they tend to result in more stable dispersions. Concentrated stock dispersions may be diluted with water or acidified water for subsequent use.

The dispersions of the present invention have a positive electrostatic charge much stronger than that of dispersions prepared with either component alone. Thus, they are particularly useful in a wide variety of electrostatic charge neutralization techniques used to treat negatively charged materials such as pitch in pulp and paper mills, latex, gums, primary and secondary sewage, and the like. As little as about .03 to .3 lbs. of alumina per ton of stock is generally effective, preferably at a pH of about 3 to 6.

The compositions of the present invention are useful in imparting anti-slip friction surfaces to material such as papers, particularly highly calendered papers, but including coated and impregnated papers, fiber glass, textiles, some plastics and metals. Dispersions of about 0.8 to 8% by weight can be applied to such surfaces by spray, roller, or sponge coating techniques known in the art, although a preferred method and apparatus for using these materials will be discussed hereinafter with respect to Example 4 and Table 5.

Having now generally described the invention, it is believed that those skilled in the art can utilize it to its fullest extent. The following Examples are accordingly presented as illustrative and not limiting of the remainder of the disclosure.

Table 1 sets forth physical characteristics of the alumina compositions used in the following Examples, together with characteristics of a fumed silica composition used as a comparison.

TABLE 1 Composition A B C D (Alu- (Di 1 (Al s a on o M) p C) C) (OX-50 Type of product Alumina. Alumina. Alumina. Silica. Surface 0 arge (Dispersed) Alumina tiaylpei .z.-.).-. 4Agspham. gamma 21?}elta. A artcesze mu 13%. surtace area 320 100 50.

(m. /gm.). Aluminagontent (dry 99% 99% 97%."... (810' 99.8%).

reen p of 4% aqueous it 4.4 4.5 3.8-4.6.

I With acid added.

Slip angles were determined after non-skid application by the modified Meyer 16 method. The board to be treated is cut into 4 inch wide strips approximately 3 feet long and placed in an oven and pre-heated to about F. to simulate corrugator plant conditions. A 4" x =24" x cellulose sponge is soaked in a 10/ 1 dilution of solution and then when saturated it is squeezed around in a U shape until the excess liquid runs out. The board is then taken out of the oven, laid flat on a table and held firmly in place by clamps. The wet sponge is placed on the bottom of the board in front of an i mil Meyer Rod along with a piece of wood to push the spongeinto the rod. The board is then coated by running the Meyer Rod and sponge up the board in one quick motion, while squeezing the sponge so that the nip between the Meyer Rod and board is always flooded. The board is then held upside down to drain any excess liquid, and let dry in the air. In this manner a very dilute solution of non-skid is applied very evenly and uniform slip angle results are obtained by a Key slip angle tested.

EXAMPLE 1 Comparative tests of pitch neutralization were performed by standard method on representative individual alumina compositions and mixtures thereof according to the present invention. 20 ml. samples of a 0.1% pitch dispersion taken from a paper mill were treated with varying volumes of 1% alumina solids dispersions to flee the pitch, the resulting mixtures filtered, and the filtrate examined visually for clarity. A clear filtrate indicates complete neutralization of the pitch particles and resulting floc formation which is filtered out. Results are presented in Table 2.

TABLE 2 Filtrate appearance 37.5% "A Alumina "A" Alumina 13" 62.5% B

cc. of 1% alumina solids per 20 cc. 1% pitch dispersion:

10 cc Pretty cloudy..... Clear Clear. or fin V. slightly cloudy... Do. 2 no e do Fairly cloudy Do. 1 cc Very cloudy ..do....- Slightly cloudy. Expected neutral point"--- cc 10 cc cc.

The above results indicate that alumina mixtures of the present invention have a much higher electrostatic charge than either of the component materials alone, since only 20% as much of the mixture was required to reach an end point, as compared to the most effective individual component.

EXAMPLE 2 This Example illustrates the improved slip angles obtained on corrugated paper using the compositions of the present invention. All slip angles 'were measured at sliding pressures of 69 gm./sq. in. using the Meyer 16 method to apply the composition, and represent an average of at least six applications. All dispersions had a total solids content of 3.92 weight percent. Results are summarized in Table 3 and graphically illustrated in the figures.

It can be seen from the following data that improved slip angles are obtained only by mixtures of different aluminas having the necessary properties such as particle sizes and surface areas as described herein.

TABLE 3 Avg. slip angle, Proportion of ingredients degrees FIGURE 1 CURVE A Alumina B Silica D FIGURE 1 CURVE B Alumina B Alumina C FIGURE 2 CURVE C Alumina A Alumina B FIGURE 2 CURVE D Alumina A Alumina C EXAMPLE 3 Using the following formulation, slip angle tests were conducted as described above on board and paper coated with various dilutions of the basic formulation in actual plant tests.

TABLE4 Shipping cartons Bags Kraft Mottled Plain 'Prlnted Dilution with water [EXAMPLE 4 Using a 1:4 aqueous dilution of the composition of Example 3, 50 lb. Kraft liner board was coated using the method described in our copending U.S. Patent Application Ser. No. 201,900, filed of even date with this application and entitled Method and Apparatus for Applying Anti-Slip Agents," now abandoned, the disclosure of which is incorporated by reference. Briefly, the technique described therein involves spraying onto an applicator roller at an angle of to 270 from the nipfat the top, and passing the board over the top thereof to apply an even film of anti-slip agent to the board. By spraying onto a roller away from the nip, much better results are obtained than by spraying directly into the nip. Table 5 illustrates results obtained by this method.

TABLE 5 Board Spray Top speed, pressure, Slip roller i.p.m. p.s.i. angle It will be appreciated that while the foregoing examples are directed .to preferred embodiments of this invention, it is capable of numerous alterations or modifications as will be apparent to those skilled in the art.

What is claimed is:

1. A positively charged colloidal aqueous mixed alumina dispersion comprising:

(a) 25 to 75% by weight of the total alumina of a first alumina composition having an ultimate dispersed particle size no more than about one-fifth as great as a second alumina composition; and

(b) correspondingly 75 to 25% by weight of said second alumina composition, said second alumina composition having a particle size of about 10 to mu.

2. A dispersion according to claim 1, wherein said first alumina composition has a particle size of about 2 to 10 m and said second alumina composition has a particle size of about 10 to 100 m 3. A dispersion according to claim 2 wherein said first alumina composition has a particle size of about 4 to 6 m and said second alumina composition has a particle size of about 20 to 30 my 4. A dispersion according to claim 1, wherein said first alumina composition comprises an alpha alumina and said second alumina composition comprises a gamma or delta alumina.

65% by weight of the total alumina content. 5 6. A dispersion according to claim 5 wherein s ai d first) and second alumina compositions are present in equal proportions.

7. A dispersion according to claim 1, wherein said first and second alumina compositions form a total solids i v JOHN E PrimaryExaminer content of 1 to 15%.

8. A dispersion according to claim 1 wherein said first alumina "composition comprises an alpha aluminaand said second alumina composition comprises a gamma or delta alumina, said-first and-second alumina-compositions forming a total solids content .of about 1 to 15%.

References Cited UNITED STATES PATENTS- 2,931,779 4/1960 White 252-313 R I us. (:1, X.R. 111-452; 162-181; 252317 

